From be5288abc0f028f2d284807dfda17e82891569d2 Mon Sep 17 00:00:00 2001 From: xiaojin Date: Mon, 13 Aug 2012 13:43:15 +0100 Subject: [PATCH] n_gsm.c: Implement 3GPP27.010 DLC start-up procedure in MUX commit 7e8ac7b23b67416700dfb8b4136a4e81ce675b48 upstream. In 3GPP27.010 5.8.1, it defined: The TE multiplexer initiates the establishment of the multiplexer control channel by sending a SABM frame on DLCI 0 using the procedures of clause 5.4.1. Once the multiplexer channel is established other DLCs may be established using the procedures of clause 5.4.1. This patch implement 5.8.1 in MUX level, it make sure DLC0 is the first channel to be setup. [or for those not familiar with the specification: it was possible to try and open a data connection while the control channel was not yet fully open, which is a spec violation and confuses some modems] Signed-off-by: xiaojin Tested-by: Yin, Fengwei [tweaked the order we check things and error code] Signed-off-by: Alan Cox Signed-off-by: Greg Kroah-Hartman --- drivers/tty/n_gsm.c | 4 ++++ 1 file changed, 4 insertions(+) diff --git a/drivers/tty/n_gsm.c b/drivers/tty/n_gsm.c index c43b683b6eb81..0a73b59f797d6 100644 --- a/drivers/tty/n_gsm.c +++ b/drivers/tty/n_gsm.c @@ -2889,6 +2889,10 @@ static int gsmtty_open(struct tty_struct *tty, struct file *filp) gsm = gsm_mux[mux]; if (gsm->dead) return -EL2HLT; + /* If DLCI 0 is not yet fully open return an error. This is ok from a locking + perspective as we don't have to worry about this if DLCI0 is lost */ + if (gsm->dlci[0] && gsm->dlci[0]->state != DLCI_OPEN) + return -EL2NSYNC; dlci = gsm->dlci[line]; if (dlci == NULL) dlci = gsm_dlci_alloc(gsm, line); -- 2.47.2